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Why do pots and pans turn grayish or black?
Aluminum pots and pans turn a grayish/black when water is boiled in them or a low-acid food is cooked in them. This is from the formation of metallic oxides. When an acid food is cooked in the pots, the acid dissolves the oxides and the pan brightens again. To brighten a pan without cooking an acid food in it, boil a solution of cream of tartar in it until brightening occurs. (2 Tablespoons cream of tartar per quart of water.) The discoloration is not harmful. It is an aesthetic concern, only. PREPARED BY: Angela M. Fraser, Ph.D., Associate Professor/Food Safety Specialist, and Carolyn J. Lackey, Ph.D., R.D., L.D.N., Professor/Food and Nutrition Specialist, North Carolina State University (August 2004)